1. Field of the Invention
This invention relates to a holder for a vane of a vertical venetian blind assembly used, for instance, for covering an architectural opening, such as a window or door.
2. Description of the Related Art
Vertical venetian blinds have generally been provided with horizontally-extending head rails, holding a plurality of carrier or travellers that can be moved in spaced apart relationship along the longitudinal length of each head rail. Each carrier has typically supported a vertically-extending louver, slat or vane by a vane holder in such a manner that the user of the vertical blind can move the vane along the length of the head rail (e.g. by pulling on a first operating cord or pull cord) and also can rotate or tilt the vane about its vertical axis (e.g. by pulling on a second operating cord or tilt cord). For this purpose, each carrier has typically included a main body with a vertically oriented drive hub or worm wheel, which is drivingly connected to a worm gear. The bottom of each drive hub has supported a depending vane holder, adapted to hold securely the top of a vane. A horizontally-extending tilt rod or drive shaft has been provided in the head rail, extending through the carriers and engaging their worm gears, whereby rotation of the tilt rod about its longitudinal axis has caused the drive hubs of the carriers to rotate about their vertical axes so as to make the vane holders and the attached vanes tilt together.
A problem in mounting a vertical venetian blind in a slanted or sloped architectural opening is that, for each slope angle, different vane holders are required. Specifically, a suitable length has to be chosen for each related slope under which the blind is mounted, since the length of the vane holder influences the space the vane of the blind has for rotating and thus tilting. The steeper the slope, the longer the vane holder has to be. When the vane holder is too short, the upper marginal portion of the vane hits the head rail when rotated. When the vane holder is too long, it negatively influences the look of the blind, because light will leak into the room even when the blind is closed. Generally, a blind manufacturer will offer a limited number of different length vane holders. For slopes that are not covered in the assortment of vane holders, a compromise can be made by using a vane holder of a length that comes closest to the ideal one. So in practice, vane holders of a specific length will be used for a range of slope angles. This is not ideal and will lower the quality of the product. The same problem occurs with blinds that are to be mounted in arched or curved architectural openings.
U.S. Pat. No. 6,000,456 solves a different problem, based on a difficulty that can be encountered when mounting a vertical blind assembly adjacent an architectural opening. In particular, where the vanes of the vertical blind assembly are of a particular length, it is necessary that the head rail is positioned and mounted accurately relative to the architectural opening. If the head rail is mounted too high or too low, it becomes necessary to remount it, possibly causing undesirable damage to the architectural opening surrounding. As a solution to this problem, U.S. Pat. No. 6,000,456 proposes a vane holder having an adjustable length. The vane holder has a vane clasp and a clasp holder, the vane clasp having a first end, to which the vane of the blind is attached, and a second end which can be attached to the clasp holder. The holder, in turn, can be attached to a carrier of a vertical blind. The second end of the clasp has ratchet grooves, each of which can co-operate with a single locking tooth in the holder, such that a resilient ratchet-type mechanism is created. The clasp can be moved resiliently between engaging consecutively one of the securing points or ratchet grooves to the locking tooth in the holder so as to vary the height of the vane.
The length adjustable vane holders of U.S. Pat. No. 6,000,456 could theoretically solve the problem of for sloped vertical blinds. Unfortunately, this is not the case since such holders were originally designed only for correcting small inconvenient differences in length. Also a drawback of the adjustable ratchet of such holders is that it is difficult to control their adjustment. In order to overcome the connection between the operably engaged ratchet parts of these holders, one generally has to pull on them, but it is not uncommon that too much force is used and thereby the desired length of the holders is exceeded. This is because the correct amount of force is difficult to control.